1. Field of the Invention
The invention is directed to the telomerization of a conjugated alkadiene with organic hydroxy compounds in the presence of a catalyst to produce an organo-oxyalkadiene.
2. Background of the Prior Art
The telomerization of conjugated alkadienes with alkanols by means of palladium catalysts is a convenient route for the preparation of alkoxy alkadienes such as the reaction of butadiene with methanol to produce 8-methoxy-1,6-octadiene. Because of the high cost of palladium catalyst, any industrial process employing catalysts of this type requires recycling of the catalyst in order to minimize the cost of production. Accordingly, catalyst recovery and recycle is of primary concern along with selectivity, yields and speed of reaction in the selection of a catalyst for telomerization reactions of this type. Although palladium type catalysts are effective in promoting these types of telomerization reactions, after recovering and recycling the catalyst for subsequent reactions, it has been observed that the activity of the catalyst drops off significantly. Additionally, prior to recovering and recycling the catalyst, the various products of the telomerization reaction must be separated by a process which does not substantially damage or deactivate the catalyst or cause a loss of the catalyst. The prior art method of recovering the telomerization product generally comprised distillation of the reaction product to remove them from the catalyst and resulted in catalyst loss and/or deactivation.
Typical of the prior art processes involving the reaction of conjugated alkadienes with alkanols in the presence of a palladium catalyst are U.S. Pat. Nos. 3,670,032 and 3,769,352 both issued to Romanelli. The process of these patents utilize a zero valence palladium catalyst including a non-ionic ligand. Such a catalyst system is soluble in non-polar organic solvents, such as hydrocarbons, as is the unsaturated alcohol or ether product. The problem with the use of these catalysts lies in the separation of the catalyst from the product. Such separation occurs by distillation. As stated above, this separation is characterized by catalyst deactivation and/or loss.
An attempt to overcome the difficulties occasioned by the use of non-ionic ligands is illustrated by U.S. Pat. No. 4,142,060 issued to Kuntz. In Kuntz the palladium catalyst system employs an ionic ligand which is soluble in the protic polar solvent used therein, water. As such, the catalyst is almost completely separated from the diene product by phase separation. However, this solution creates other difficulties. If, as Kuntz proposes in one preferred embodiment, water is added as solvent before or during the reaction, the preferential solubility of the palladium catalyst system in water, while the reactants are in the non-polar organic phase, leads to low rate of reaction due to poor contact between the reactants and the catalyst. If, on the other hand, water is added after the reaction is complete, a new problem, the separation of the catalyst from the water, arises. Such a problem is very similar to the difficulty of separating the catalyst from the non-polar solvent encountered in art exemplified by the Romanelli patents. Of course, if no attempt to separate the catalyst from the water is made, then upon recycle the problem recited above, directed to the case where addition of water occurs before the reaction, ensues. Upon recycle the rate of reaction decreases because of the separation of the catalyst, in the polar phase, from the reactants, in the non-polar organic phase.
Even if the Kuntz disclosure employs a miscibilizing solvent to overcome the problem of catalyst-reactant separation during the reaction a new problem is presented. The miscibilizing solvent must be removed by distillation. This additional operation adds a difficult complication to the telomerization process.
Accordingly, it is an object of the present invention to overcome these and other difficulties encountered in the prior art.
It is a further object of the present invention to provide a method for the telomerization of a conjugated alkadiene with an organic hydroxy compound to produce an organo-oxyalkadiene.
It is also an object of the invention to provide a process for conducting the aforesaid telomerization reaction by means of a palladium-type catalyst and which process provides a novel method for separating the organooxyalkadiene from the catalyst so that the catalyst can be recycled without substantial catalyst loss or substantial loss of catalyst activity.